In recent years, an IC tag and a non-contact IC card carrying out transmission and reception of an electromagnetic wave signal given by a reader/writer in a non-contact fashion have been developed and put in practical use. As a planar antenna in which an antenna circuit pattern (a circuit pattern) of such non-contact IC card and IC tag is formed, a planar antenna is proposed having a circuit pattern comprised of an antenna part and a connecting terminal part on a resin film and in which the circuit pattern has a metal layer and a heat-sealable conductive layer provided on the top surface of the connecting terminal part of the metal layer (for example, Patent Document 1). This technique is advantageous for reducing cost because it enables an electronic part such as an IC chip to directly connect to the conductive layer without using wire bonding, an anisotropic conductive film (ACF) and the like used in a conventional technique. In this technique, a planar antenna is produced on a resin film with a step (a) of providing a metal layer that constitutes a circuit pattern comprised of an antenna part and a connecting terminal part on a resin film, a step (b) of providing a protective layer on a portion constituting the antenna part of the metal layer, a step (c) of providing a heat-sealable conductive layer on a portion that constitutes the connecting terminal part of the metal layer, and a step (d) of removing a portion that does not constitute the circuit pattern of the metal layer by etching after the step (b) and the step (c). That is, the portion covered with the protective layer serves as the antenna part of the circuit pattern, and the portion covered with the conductive layer serves as the connecting terminal part of the circuit pattern.    Patent Document 1: International Patent Application Laid-Open No. 2006-103981 (Claims)